To meet the demand for wireless data traffic having increased since deployment of 4th generation (4G) communication systems, efforts have been made to develop an improved 5th generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post Long Term Evolution (LTE) System’.
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.
In the 5G system, Hybrid frequency shift keying (FSK) and quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
Also, in modern society, electronic devices are used for various communications. Further, the growth of communication technologies results in the implementation of wireless communication based services in various electronic devices. In accordance with this, the kind of electronic devices including antennas for wireless communication is being gradually diversified. Physical space securing is essential for antenna performance securing. Generally, the antennas have the maximum performance at a size of λ/2 or λ/4. The λ means a wavelength at an operation frequency. However, in some cases, the size of the antenna is designed much smaller than the wavelength. Generally, the antenna of the size much smaller than the wavelength is called a ‘small antenna’. At this time, the performance of the small antenna is proportional to a size of the antenna.
In case where a communication band is within a range of 700 MHz to 3000 MHz, the 700 MHz being a low band frequency has a wavelength of about 40 cm. For example, in case where a communication band of a portable terminal (e.g., a smart phone) is the 700 MHz, a space to install the antenna of the 40 cm size is not permitted. Accordingly, in a case of the low band, an antenna built in the portable terminal corresponds to a small antenna. Recently, portable terminals are on the trend of thickness decrease, screen increase, bezel decrease, etc. and accordingly to this, a space capable of mounting antennas is gradually decreasing. Furthermore, owing to the multi-functionality of the portable terminals, the number of parts mounted therein increases, and the securing of the space for mounting the antennas is getting more difficult.